Background: This study aimed to evaluate the dose calculation accuracy of Eclipse^TM treatment planning system (TPS) in a heterogeneous chest phantom with the intensity modulated radiotherapy (IMRT) technique using EBT3 film and Delta4. Materials and Methods: Two IMRT plans (A and B) were prepared for radiotherapy of the heterogeneous chest phantom. Plan A was between the left lung and the surrounding soft tissue and plan B was carried out on the soft tissue. EBT3 film and Delta4 were used for dose measurement in the phantom. Eclipse^TM TPS was also used for dose calculation. Finally, the gamma index values of the TPS with film and TPS with Delta4 were obtained. A 95% passing rate of gamma index with the passing criterion of 3mm/3% and a dose threshold of 20% as the standard criterion was considered in this study. Furthermore, the passing rates of gamma indices of the film and Delta4 were compared with each other via Bland-Altman analysis. Results: The mean passing rate of gamma index with standard passing criterion between the TPS calculations and film measurements was 96.95±0.22%, while it was equal to 97.7±0.56% and 98.45±0.21% between the TPS calculations and 2D and 3D Delta4 measurements, respectively. Additionally, the differences between the passing rates of gamma indices of the film and Delta4 were less than 5%. Conclusion: The findings demonstrate that the accuracy of dose calculations of Eclipse^TM TPS in a heterogeneous chest phantom with the IMRT technique is within the standard passing criterion. Furthermore, it can be concluded that there is a good agreement between the film and Delta4, as IMRT QA devices.